Liquefied gas conveyor

ABSTRACT

Un-pressurized liquefied gas (LNG) is transported at high speed in elongated end-to-end connected insulated pressure containers attached to an in prior art disclosed bulk material conveyor having an endless chain of long links in end-to-end relationship for high speed. A folding mechanism turns links into vertical side-by-side relationship for filling and discharge at low speed. In absence of refrigeration means on board, an attached gas return pipe collects from containers in transit re-gasified portions of LNG and gas emitted during filling and discharge, and returns it for re-liquefaction or other use. Containers are capable of holding gas under pressure in case of extended conveyor stoppage. Under no circumstance is gas released to the outside. High conveyor speed is enhanced with magnetic levitation suspension and linear induction motor propulsion.

BACKGROUND OF THE INVENTION

The present invention relates to design and construction of a liquefied gas-carrying adaptation of the principle mode and mechanism of an in prior art disclosed “Bulk Material Conveyor”, U.S. Pat. No. 4,024,947. More specifically it relates to container design, method of filling, emptying and transporting liquefied gas (LNG) safely and without undue re-gasification or boil-off loss in transit. Furthermore, container design and attached piping feature recovery and recycling of in transit re-gasified fluid and other emitted gas.

In general, a liquefaction plant liquefies gas by cooling it to below −260° F. (−160° C.). Elongated containers are then dynamically filled with LNG while in side-by-side upright position, similar to filling bottles by conventional bottling machines. Thereafter, containers are sealed, rotated into horizontal end-to-end position and rapidly transported by the conveyor to their destination where they are returned into the same side-by-side upright position and siphoned empty. Any in transit re-gasified LNG, which may occur during extended conveyor stoppage, as well as other residual gas, is recovered and returned in returning empty containers and by a gas return pipe to the filling end of the conveyor for re-liquefaction, or it is made available for other use at both ends and alongside of the conveyor.

SUMMARY OF THE INVENTION

The present invention provides the ability to carry LNG by a conveyor of a type having in a closed loop an endless string of elongated containers traveling at relatively high rate of speed between a filling end and a discharge end, containers being folded into vertical side-by-side relationship at relatively low rate of speed for filling at filling end and for discharge by means of siphoning at discharge end. Containers have two walls separated by insulating or vacuum space, an outer wall to provide physical strength, propulsion, guidance and connection to adjacent containers, and an inner wall to contain LNG, normally un-pressurized but when necessary under high pressure. When in folded upright relationship, upper ends of containers reveal two access ports, one for fluid filling and discharge, and the other for gas release. Containers are equipped with safety gas-only pressure release valves, which are connected to an attached endless flexible gas return pipe. Discharge of gas from containers is transmitted by the gas return pipe back to the liquefaction plant or it is made available for other use. The flexibility of the gas return pipe allows it to bend with containers as they fold and unfold at filling and discharge ends. Said LNG transporting conveyor comprising:

-   -   (a) means for holding LNG in heat shielded and physically         protected pressure containers;     -   (b) means for in transit re-gasified fluid to be recovered for         either re-liquefaction or other use;     -   (c) means for limiting accidental loss;     -   (d) means for supplying gas as fuel to propulsion booster         stations along the way.

The present invention is intended to enable transportation overland of LNG in large quantities, similar to what is already commonly done by ship at sea. The advantage of liquefaction is that gas volume is thereby reduced by a ratio of about 620 to one. While LNG ships take many days for a single delivery, they have on board refrigeration machines to prevent re-gasification of their cargo. Re-gasification expands LNG back to its original volume, except when it is confined in pressure containers. The present invention has no refrigeration machines traveling with its containers. Instead it relies on delivering un-pressurized LNG at high rate of speed, thereby leaving very little time for temperature increase and re-gasification in transit. To enable high speed, wheels as means of suspension are replaced with permanent magnets in repulsion, and gears as means for propulsion are replaced with linear induction motors. Due to the use of siphoning as unloading means, turning containers upside down between loading and unloading ends of conveyor, as described in prior art, is eliminated.

Large quantities of stranded natural gas in remote regions could be brought as LNG to market with this invention, for example, from the North Slope of Alaska for a distance of 800 miles (1,300 Km) to a shipping port in the south of Alaska. With a line speed of 200 miles/hour (320 Km/hour), containers would be exposed for four hours to re-gasification inducing surroundings, which with pre-cooling of LNG to lower than re-gasification temperature and with good insulation or vacuum, as used in vacuum flasks, would keep heat intrusion and re-gasification to a minimum. However, the present invention provides that any emitted gas due to re-gasification and excessive container pressure would be recovered and returned for re-liquefaction by the endless gas return pipe to which all containers are connected. No gas would be released to the outside. In case of an accident, only directly affected containers could break open. Spilled contents would quickly evaporate. The gas return pipe attached to the sides of containers is fitted at intervals with pressure surge shutoff valves, which would limit gas loss in case of pipe fracture.

For a shorter application, the present invention could also be used as an LNG land bridge across Panama similar to what already exists for crude oil. Many new LNG ships are now also too large to fit through the Panama Canal. LNG re-gasification boil-off while in transit may be reduced or even totally avoided by (1) pre-cooling containers before filling, (2) filling containers only partially and (3) replace long conveyors with shorter ones interspaced with liquefaction booster plants.

BRIEF DESCRIPTION OT THE FIGURES

FIG. 1 shows a cross-section of an LNG container with gas return pipe.

FIG. 2 shows a layout of an LNG conveyor.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a typical cross-section of container 1. It is cylindrical in shape and has an outer wall 2 and an inner wall 3 separated evenly all around by insulating material or vacuum 4. The center of container 1 contains LNG 5. Outer wall 2 is attached to a link of a bulk material conveyor having an endless chain with elongated links guided at high speed with links in end-to-end relationship and at slow speed with links in folded side-by-side relationship. Inner wall 3 provides ability to withstand high pressure. All containers 1 are connected via gas-only pressure release valves 6 to attached endless flexible gas return pipe 7, which is fitted at intervals with pressure surge valves to limit loss of gas in case of pipe fracture.

FIG. 2 shows a plan view of a typical LNG conveyor 8. Progressing slowly through circular filling end 9 are containers 1 in upright side-by-side relationship being filled with LNG 5 through openings at their tops by means similar to conventional bottling machines. Any gas expelled from containers 1 during filling is returned for re-liquefaction or other use. On arrival for filling, containers 1 are rotated in deceleration section 10 from a horizontal end-to-end relationship to an upright side-by-side relationship. The reverse rotation occurs in acceleration section 11. Thereafter, filled containers 1 are propelled along guideway 12 and empty returns along guideway 13. Arriving for discharge, filled containers 1 are rotated again into upright side-by-side relationship in deceleration section 14. Containers 1 are emptied by means of inserted siphoning tubes as they pass at low rate of speed through circular discharge end 15 before unfolding again in acceleration section 16. As a safety precaution, to prevent air from intruding into containers 1, which could create an explosive mixture, 

1. A method for transporting liquefied gas (LNG) in end-to-end connected elongated containers guided and propelled by the mechanism of an in prior art disclosed closed loop conveyor having folding and unfolding links to achieve a low rate of speed for filling and discharge, and a high rate of speed in-between.
 2. A method of claim 1 wherein incidentally re-gasified portions of LNG from containers and incidentally to filling and discharge emitted gas is recovered for re-liquefaction or for other use.
 3. A method of claim 2 wherein all containers are connected through gas-only pressure release valves to an attached endless flexible gas return pipe.
 4. A device for transporting LNG in end-to-end connected elongated containers guided and propelled by the mechanism of an in prior art disclosed closed loop conveyor having folding and unfolding links to achieve a low rate of speed for filling and discharge, and a high rate of speed in-between, said device comprising: (A) elongated cylindrical double-walled insulated pressure containers with outer walls providing guidance, controls and connection to adjacent containers and inner walls providing containment for LNG; (B) gas and LNG access ports on containers for mating with filling and emptying nozzles at filling and discharge ends of conveyor; (C) means at filling and discharge ends of conveyor for supplying to, and withdrawing from, containers through flexible temporary hookups gas and LNG.
 5. A device of claim 4 wherein incidentally re-gasified portions of LNG from containers and incidentally emitted gas during filling and discharge is recovered for re-liquefaction or for other use.
 6. A device of claim 4 wherein all containers are connected through gas-only pressure release valves to an attached endless flexible gas return pipe.
 7. A device of claim 4 wherein booster propulsion means located at intervals along the conveyor are supplied with gas for fuel during stops by temporarily connecting to the gas return pipe. 